bachelor thesis in aeronautical engineering 15 credits, basic level 300

151 Pages·2011·4.38 MB·English

School of Innovation, Design and Engineering
BACHELOR THESIS IN
AERONAUTICAL ENGINEERING
15 CREDITS, BASIC LEVEL 300

Aerodynamic Investigation of Air Inlets on Aircrafts with
Application of Computational Fluid Dynamics

Author: Marcus Lejon
Report code: MDH.IDT.FLYG.0233.2011.GN300.15HP.Ae

Abstract
Air inlets in some form are used on all commercial airliners today. The type of air inlet investi-
gatedinthisreportisaNACAinletsubmergedintoasurface. Thissurfaceiswithinthisthesisa
testsectionwallofawindtunnel. TheconsideredwindtunnelisTWGinGo¨ttingen(Germany)
that operates in transonic speeds. Submerged inlets have the main advantage of low aeroynamic
drag from the inlet itself. The importance of reducing drag, and the attention given to this sub-
jectisincreasingasfuelpricesriseaswellaspublicawarenessofenvironmentalimpactbyallofus.
The outcome of this thesis contributes to the government-funded project ECOCENTS which
deals with the design of innovative new aircraft cooling systems and the detailed flow analysis of
these systems. This thesis was carried out at the company Airbus in Bremen, Germany.
The main objective of this report was the evaluation of the ram pressure efficiency of four
different ramp angles of a NACA inlet and the estimation of the drag caused by these geome-
tries with the use of Computational Fluid Dynamics (CFD). The flow solver used was TAU, a
Reynolds-Averaged Navier-Stokes (RANS) solver developed by the German Aerospace Center
(DLR).Theinletconsistedofonerampsectionwheretherampanglewasfixedat7degrees,and
a second variable ramp section. The following different angles were investigated: 4, 7, 10 and 15
degrees. These configurations were evaluated at a velocity of Mach 0.8 and a Reynolds number
of 10·106. The ramp angle of 7 degrees was evaluated at two additional velocities (Mach 0.73
and Mach 0.87) and at two additional Reynolds numbers (5·106 and 15·106) at Mach 0.8.
The inlet efficiency outcome of this study was located between two other investigations. The
results of this RANS computation predicted a higher total pressure at the inlet throat plane
compared to a previous CFD investigation where a different RANS solver at the same geometry
was used. In comparison to an estimation method mainly based on experimental data (ESDU
method), the recent study showed a lower total pressure at the inlet throat plane. The aerody-
namic drag that arised by the presence of the inlet system was calculated within this thesis to
be higher than the outcome of the experimental data based (ESDU) method.
The advantage of using a NACA type inlet was observed to be highly related to the ramp
angle. Vortices are originated and develop along the edges of the intake ramp walls. These two
vortices help to transport higher energy flow from the free stream into the inlet and therefore
reduce the boundary layer thickness in the inlet region. For lower mass flows (0.10 - 0.20 kg/s)
a ramp angle of 7 degrees was seen to be prefered in view of ram pressure efficiency. At a higher
mass flow (0.25 kg/s) the 10 degrees ramp angle was prefered, followed by the 15 degrees ramp
angle at the highest investigated mass flows (0.30 - 0.35 kg/s). In view of drag, the lowest ramp
angle possible for a given mass flow was seen to be most advantagous.
Future work on this subject will include simulation of an inlet in combination with a heat
exchangerandaramairoutlet. Thisarrengementwillbethesameasintheinvestigationatthe
TWG test campaign and therefore comparable. The difference in outcome of the separate CFD
analysis was discussed within this investigation but could not be completely cleared.

Sammanfattning
Luftintag av n˚agot slag anv¨ands p˚a alla kommersiella trafikflygplan idag. Den typ av luftintag
som unders¨oks i den h¨ar rapporten ¨ar ett NACA luftintag neds¨ankt i en plan yta. I det h¨ar
examensarbetet ¨ar den h¨ar ytan en v¨agg i en vindtunnel. Den aktuella vindtunneln f¨or den h¨ar
studien ¨ar TWG i G¨ottingen (Tyskland) som kan simulera luftfl¨ode i det transoniska omr˚adet.
Neds¨ankta luftintag har f¨ordelen med ett l˚agt luftmotst˚and orsakat av sj¨alva luftintaget. Vikten
av att reducera luftmotst˚and ¨okar i takt med stigande br¨anslepriser och ¨okad medvetenhet om
v˚ar inverkan p˚a milj¨on.
Resultaten fr˚an det h¨ar examensarbetet bidrog till det myndighetsfinansierade projektet
ECOCENTS som handlar om design av innovativa nya kylsystem f¨or flygplan samt ing˚aende
analyser av luftfl¨odet i dessa system. Det h¨ar examensarbetet utf¨ordes p˚a f¨oretaget Airbus i
Bremen, Tyskland.
Det huvudsakliga m˚alet med den h¨ar rapporten var att g¨ora en utv¨ardering av effektiviteten
hosfyraolikavinklaravdenrampsomledernertillluftintagetsamtluftmotst˚andetsomorsakas
avdessamedhj¨alpavComputationalFluidDynamics(CFD).Detprogramsomanv¨andesf¨oratt
utfo¨raber¨akningarnaheterTAUoch¨arenReynolds-AveragedNavier-Stokesl¨osareutveckladav
GermanAerospaceCenter(DLR).Luftintagetbest˚aravenrampsektiond¨arvinkelnmellanram-
pen och ytan som luftintaget ¨ar neds¨ankt i ¨ar konstant 7 grader, och en sektion d¨ar vinkeln kan
¨andras. F¨oljande vinklar unders¨oktes: 4, 7, 10 och 15 grader. Dessa konfigurationer utv¨arderas
vid en hastighet av Mach 0.8 och ett Reynolds tal p˚a 10·106. Rampen med en vinkel p˚a 7
grader utv¨arderades vid ytterligare tv˚a hastigheter (Mach 0.73 och Mach 0.87) och ytterligare
tv˚a Reynolds tal (5·106 och 15·106) i Mach 0.8.
Effektiviteten hos luftintaget ber¨aknades i den h¨ar studien till att ligga mellan tv˚a andra
unders¨okningar. Resultaten fr˚an RANS-ber¨akningar uppskattade ett h¨ogre totaltryck vid ”inlet
throat plane” j¨amf¨ort med en tidigare unders¨okning gjord p˚a samma geometri med ett annat
program f¨or RANS-ber¨akningarna. I j¨amf¨orelse med en metod baserad p˚a experimentella resul-
tat (ESDU metoden), s˚a visade studien i det h¨ar examensarbetet p˚a ett l¨agre totaltryck. Det
luftmotst˚andsomuppst˚arp˚agrundavluftintagetochtillh¨orandekomponenteravluftintagssys-
temet ber¨aknas i det h¨ar arbetet till att vara h¨ogre ¨an den uppskattning som gjordes baserad p˚a
experimentella data (ESDU).
F¨ordelen med att anv¨anda ett NACA luftintag observerades vara n¨ara relaterad till ram-
pvinkeln hos luftintaget. Luftvirvlar bildas och utvecklas l¨angs de ¨ovre kanterna till v¨aggarna
av rampen. De h¨ar tv˚a luftvirvlarna hj¨alper till att f¨ora luft med h¨ogre energi fr˚an fristr¨ommen
ner i luftintaget och d¨arf¨or ¨aven reducera tjockleken hos det gr¨ansskikt som finns i luftintaget.
F¨or l˚aga massfl¨oden (0.10 - 0.20 kg/s) s˚a var en konstant 7 graders rampvinkel den optimala
konfigurationen med avseende p˚a effektivitet. Vid ett h¨ogre massfl¨ode (0.25 kg/s) s˚a presterade
10 graders konfigurationen b¨ast, f¨oljt av konfigurationen med en 15 graders rampvinkel f¨or de
h¨ogsta massfl¨odena som unders¨oktes (0.30 - 0.35 kg/s). Med avseende p˚a luftmotst˚and s˚a var
alltid en s˚a liten vinkel som m¨ojligt det mest f¨ordelaktiga alternativet.
Framtida arbete kring det h¨ar ¨amnet kommer att involvera simulering av ett luftintag i
kombination med en v¨armeva¨xlare och ett luftutbl˚as. Det h¨ar arrangemanget kommer att vara
desamma som unders¨oks vid TWG och resultaten ¨ar d¨arf¨or j¨amf¨orbara. Skillnader i resultaten
fr˚andeolikaCFDanalysernadiskuteradesmenkundeinteredasutheltidenh¨arunders¨okningen.

Date: 8 July 2011
Carried out at: Airbus Operations GmbH
Supervisor and Examiner at MDH: Gustaf Enebog
Lecturer and Program Coordinator of the
Bachelor Program in Aeronautical Engineering
School of Innovation, Design and Engineering
M¨alardalen University
Email: [email protected]
Advisor at Airbus: Udo Krause
Research Engineer in Aircraft Aerodynamic Design
Aerodynamics Department - EGACAB
Airbus Operations GmbH
Email: [email protected]

Acknowledgements
I would like to thank Udo Krause for all his help with this thesis and for making me feel very
welcome to Germany and the Airbus company.
Thank you to Bruno Stefes who shared his expertise on intakes and aerodynamics in general.
Thank you to everyone at the Aerodynamics department at Airbus in Bremen for being very
friendly and giving me a good place to perform my studies.
Thank you to Linda van Leeuwen, my partner, who has been very supportive during this under-
taking.